1. Field of the Invention
The invention relates to a process for preparing a low fat spread wherein the original oil-in-water emulsion has been completely converted to the water-oil-in form.
2. The Prior Art
Health and calorie consciousness among the public has prompted manufacturers to introduce spreads at different fat contents. Thus, in the past ten years spreads containing fat levels of 45-75%, as against 80% or 40%, have appeared on the market. The majority of these are soft products filled in plastic tubs. At the higher fat contents, these products have excellent oral properties, comparing very favorably with conventional 80% fat products. At lower fat levels, the organoleptic properties are compromised because of high water content. This aspect is most pronounced with stick products.
Modifications of the water phse by use of starch, gelatin, gums and similar thickeners have led to improved organoleptic properties for oil-in-water emulsions. Illustrative of this technology is U.S. Pat. No. 4,238,520 to Miller et al. and U.S. Pat. Nos. 4,292,333, 4,273,795, 4,273,790 and 4,468,408 all to Bosco et al. Fat continuous phase products are reported in U.S. Pat. No. 4,366,180 (Altrock et al.) and U.S. Pat. No. 4,515,825 (Moran et al.) as being obtained by dispersing an oil-in-water emulsion into a fat phase or into a water-in-oil emulsion. Emulsifier systems have also been changed in an attempt to improve oral behavior of low fat spreads. For instance, U.S. Pat. No. 3,889,005 (Brammer et al.) and U.S. Pat. No. 4,115,598 (Moran et al.) report taste improvements with a mixture of saturated and unsaturated monoglycerides in low calorie spreads.
U.S. Pat. No. 4,555,411 (Moran et al.) describes producing a water-in-oil spread starting from an oil-in-water dairy cream by shearing and cooling the dairy cream in the absence of a cream/air interface and where the apparatus has been internally coated with a hydrophobic material. Successful inversion of the emulsion occurs to provide the final oil continuous spread.
U.S. Pat. No. 4,362,758 (MacNeill et al.) reports subjecting an oil-in-water emulsion to cooling and working in at least one scraped-surface heat exchanger to crystallize at least part of the fat. The partially crystallized emulsion is then pumped to a variable-speed crystallizing unit rotating at 600 rpm for a residence time of 100 seconds to obtain a water-in-oil spread. The patent notes, however, that small traces of water may remain unemulsified in this treatment which then requires re-working of the product.
U.S. Pat. No. 4,307,125 (Amer) discloses a low fat butter with improved spreadability and containing high levels of milk solids. This product was prepared by using high levels of monoglycerides combined with hydrocolloids such as gelatin to thicken the aqueous phase. Inversion from a water to an oil continuous product was said to be induced by the working of material in a Votator.RTM. heat exchanger.
It is an object of the present invention to obtain a low fat emulsion that has both good organoleptic properties and is microbiologically stable.
Another object of the invention is to provide a process wherein a water continuous emulsion can be inverted completely to an oil continuous one with a minimum of reprocessing.
A still further object of the invention is to provide a process which reliably converts any traces of water continuous phase into an oil continuous product. In other words, a process is sought that produces an edible spread characterized by the absence of small water beads external to the fat continuous portion.
These and other objects of the invention will become apparent as further details are provided in the subsequent discussion and Examples.